This invention is concerned with improvements in the construction and method of assembly of a class of miniaturized surgical instruments primarily intended for use in cystoscopic procedures but also suitable or adaptable for other uses such as proctoscopic or bronchoscopic procedures. When adapted for urological use, such instruments are commonly referred to as "flexible instruments" because of the flexible character of the actuating rod and its sheath which permits such an instrument to be fed through a cystoscope sheath and directed in its movement by a deflecting (Albarran) bridge or other suitable means. Using the cystoscope to reveal the area under examination of treatment, the urologist directs the jaw assembly of the flexible instrument to grasp a portion of the tissue or foreign object, take a biopsy specimen, or perform certain types of corrective surgery.
The structural complexity and small size of the jaw assembly, and the manner in which such an instrument is commonly treated along with other less delicate instruments, makes such a jaw assembly particularly vulnerable to damage. Although the jaw assembly constitutes only a small part of the instrument as a whole, jaw damage renders the entire instrument inoperative and, in the past, has generally resulted in an entire instrument being discarded or returned to the manufacturer for factory repair. While hospitals, especially larger hospitals, often have facilities for making limited repairs to surgical instruments, the construction of prior flexible instruments is such that field replacement of a broken or damaged jaw assembly is virtually impossible. Thus, even if a supply of replacement jaw assemblies was available, the job of removing an old assembly and replacing it with a new one, along with the measuring, brazing, soldering, and replating operations that would normally be required, are too difficult or involved to be undertaken by most field repair facilities.
It is therefore a primary object of this invention to provide an improved surgical instrument, and its method of assembly, which permit field replacement of the jaw assembly of that instrument. Such replacement may be performed relatively quickly and easily without complex rebuilding procedures and without brazing, soldering, and replating operations.
Some of the features of the instrument which help to make it field repairable also contribute in making it less likely to become damaged or broken in the first place. For instance, breakage of an actuator rod caused by twisting of that rod is a problem virtually eliminated by the instrument construction of this invention. Also, should excessive force be exerted to urge the jaws of the instrument into closed positions, the excess force will be directed away from the jaws to the coupling of the actuator rod and plunger (where deformation of the rod may be easily repaired), thereby protecting the delicate jaws against accidental damage from the application of excessive force.
Briefly, the instrument comprises an elongated tubular sheath (which, although usually flexible, need not be so), a jaw assembly detachably connected to one end of the sheath and a fixation housing secured to the sheath's opposite end, and a plunger mounted for reciprocation in a chamber provided by the housing. The plunger has an axial bore aligned with the passage of the sheath and an actuation rod extends through the passage and bore and is operatively connected to the jaw assembly. A helical compression spring urges the plunger in a direction extending axial and outwardly from the housing chamber, and stop means are provided by the actuation rod for precisely limiting the extent of outward travel of the plunger under the influence of the spring force without at the same time preventing axial inward movement of the plunger independently of the rod and stop means. A terminal member, preferably in the form of a knob, is threadedly connected to the plunger and secures the plunger against inward axial movement independently of the rod.
In the embodiment illustrated, the stop means takes the form of an end portion of the actuation rod bent at substantially right angles to the remainder of the rod. The laterally turned end portion is received in a radial (or diametric) slot in the end of the plunger and, as already indicated, is maintained in that position by the knob. When the knob is removed, the plunger may be retracted independently of the actuation rod, thereby fully exposing the angular end portion for deactivation of the stop means either by removal, as by cutting off the perpendicular end portion, or by bending that portion back into axial alignment with the remainder of the rod. Upon such deactivation of the stop means, the actuating rod and the jaw assembly to which it is operatively connected may be separated from the remainder of the instrument. Replacement of the jaw assembly and its actuating rod involves the reverse procedure combined with the further steps of first retracting the plunger a limited predetermined distance into the housing and then temporarily holding that plunger precisely in its retracted position, preferably by means of a jig, while the new actuating rod is bent laterally to form the stop means for limiting plunger extension in the assembled instrument.
Other aspects, advantages, and objects of the invention will become apparent from the specification and drawings.